The "one-pot" synthesis of 4-methyl-2-pentanone (methyl isobutyl ketone) from acetone over PdCu catalysts prepared from layered double hydroxides

Supported PdCu catalysts prepared from layered double hydroxides (LDHs) as precursors were evaluated in the gas phase reaction of acetone with hydrogen to methyl isobutyl ketone (MIBK). Two series of catalysts containing ca. 0.2 wt.% Pd and various amounts of Cu (Cu/Pd molar ratio of ca. 0.25, 0.5 and 1) were elaborated according to different methods. One series of precursors was obtained by impregnation of calcined Mg(Al)O mixed oxide with heterobinuclear Pd_x Cu_1-x acetylacetonates. A second series of precursors was synthesized by coprecipitation of Mg/Pd/Cu/Al LDHs. After calcination, both series were reduced at 473 K. The extends of basic, acid and metal functions were evaluated through microcalorimetric adsorption of CO₂, TPD of NH₃ and TPR of H₂. It was found that the multifunctional transformation of acetone to MIBK was rate determined by the basic function. However, the way by which the catalysts were prepared, impregnation or coprecipitation, controls the extend of hydrogenated by-products, isopropyl alcohol and 4-methyl-2-pentanol. The extensive dilution by migrating MgAlO_x species onto the metallic particles makes the coprecipitated catalysts highly selective by decreasing selectively the rate of C=O bond hydrogenation.